Sector motor, direct motion rotary actuator

ABSTRACT

A two-pole armature located between two field poles provides a direct motion rotary actuator with high starting torque and angular rotation over substantially any angle angle than 180*180*Latching, non-latching, fail-safe return return motion, torque are torque are of few of the many of modes Rotary actuators Rotary widely used widely used providing angular providing angular predetermined over predetermined angles. common most common called are called rotary solenoids since linear convert linear solenoid rotary motion. Rotary motion. have solenoids number a limitations of limitations characteristics even though even have they the93 been the subject of intensive development used are large in large quantities. Rotary inefficient are noisy. Starting torque is low and ending torque is high just the opposite to that of and ideal device. idea device.

United States Patent [191 Nelson 1 Sept. 25, 1973 SECTOR MOTOR, DIRECT MOTION ROTARY ACTUATOR [76] Inventor: Victor Nelson, 25, Dix Hills, NY.

[22] Filed: June.l9, 1972 21 Appl. No.: 263,951

Related US. Application Data [63] Continuation of Ser. No. 85,415, Oct. 30, 1970,

abandoned.

[52] US. Cl. 335/253, 310/41 [51] Int. Cl. Holt 7/08 [58] Field of Search 35/229, 230, 253,

[56] References Cited UNITED STATES PATENTS l,847,0l2 2/l932 Lavet 335/230 3,597,712 8/1971 Nakagome et al 335/254 X FOREIGN PATENTS OR APPLICATIONS 318,950 9/1929 Great Britain 335/272 Primary Examiner George Harris Att0rney-Edward H. Loveman [57] ABSTRACT A two-pole armature located between two field poles provides a direct motion rotary actuator with high starting torque and angular rotation over substantially any angle less than 180 degrees. Latching, non-latch- 4 Claims, 15 Drawing Figures Patented Sept. 25, 1973 2 ShBGtS-Shflet 1 FIG 3 FIG 2 FIG 6 FIG 5 FIG 4 VVVV FIG 7 m N 0 A S EL Y VE E N I m H T R T o A T m V FIG 14 UDGKOP OZEOPWmI Patented Sept. 25, 1973 3,761,851

2 Sheets-Sheet 2 IN\ 'EN TOR.

VICTOR H. NELSON ATTORNEY TORQUE SUMMARY In its preferred form thepresent invention comprises a two pole rotor rotating between a two pole permanent magnet field. Actuating current is applied to a winding on the armature. (The positions may also be reversed with the rotor a two pole permanent magnet and the field poles electro-magnetically excited.

The simplest and most basic operation provides an 'air'rg'ular' rotation "or nearest oft6 l3'5 degrees. Starting with the rotor at say 45 above the horizontal (the line through axes of the field poles) current is applied to the rotor coils making the rotor polarity north to north and south to south with respect to the field poles. The rotor and field poles repel] each other producing a high initial rotary torque. Rotation continues as the poles turn and become unlike and thus attracting. If motion is stopped at say 45 degrees shore of horizontal alignment, the torque will still be high at the end of the rotation. If the-exciting current is now removed, the permanent magnet field poles will continue to attract the armature'poles and the rotation is latched. Reversal of motion is accomplished merely by reversing the armature current resulting in a high torque start and return to the initial position, also latching. (A similar operation results with a permanent may be excited by current supplied through a three seg ment commutator and two or three brushes.

In the drawing FIGS. 1, 2 and 3 are views of an armature and field poles with the armature shown in three significant positions.

FIGS. 4, 5 and 6 are views of field poles and an armature carrying exciting windings in three most generally useful positions.

FIG. 7 shows a structure with permanent magnet armature and an electromagnet field.

FIGS. 8, 9, 11 and 13 show various combinations of 'an'nature windings and commutator positions.

FIGS. and 12 show two possible switching arrangements with two difierent coil configurations.

FIG. I shows an armature 1 between two permanent magnet field poles, a north pole 2 and a south pole 3. Since the armature is symmetrically positioned with respect to the field poles, it will be attracted equally to both and no rotational torque will be exerted on the ar- FIG. 2 shows the armature rotated 90 from the position in FIG. I. Here again, if the armature is magnet two. pole armature and soft iron field poles wound exciting current coils.)

If the motion is stopped shore of 90 with the horizontal, the rotor will return to. its initial position automatically when the actuating current is removed. This mode of operation may be called fail-safe" since in case of power failure, the actuator returns. to a predetermined positon.

Since the rotary motion is produced directly and the starting torque is inherently high, the device is efficient and quiet in operation. Applications requiring latching operation may be carried out without the needfor holding current, and with the actuated device directly connected to the rotary actuator.

Due to its inherent properties, its similarlity to. motor action and to distinguishoverprior art rotary actuators, I, prefer tocall my new device a .sectormotor and this term will be used in the descriptions below.

The present invention. not only has. many inherent functional. advantages but it is also a. very flexible device lending. itself to many, forms and. modes of operation in addition. to. the two generally described above. Starting, transit and: ending torque can be provided to suit a particular application: by settingthe starting and ending positions by means of stops. Actuating current may be applied to start rotation and: automatically turned off at the-endof rotation; by a. switch at. the end stop position. Switches operated: over predetermined angles of rotation provide stillfurther modes of operation. One variation of. the device comprisestwo windings on the armature, one a high: current winding for providing high rotational torque and the other a. low current winding for providing holding torque. Still another variation comprises. two windings on. the armature which aresimilar but wound in-opposite directions to provide-forwardand return torque. These windings precisely centered with respect to the field poles, equal forces will be exerted and no rotational torque will be produced. However, this position is inherently unstable, since the slightest movement in either direction will result in an unbalance of forces and the amature will be pulled one way or the other and come to rest at either the position of FIG. 1 of the oppositely directed position of FIG. 3.

FIG. 3 shows the armature rotated lfrom the position shown in FIG. ll. This again is a stable position.

It can be seen from FIGS. 1, 2 and 3 that if a winding is provided on armature I and current is passed through this winding that an interaction will take place between the field of the permanent magnet field poles and the flux produced by the current. Depending on the direction of the current, the armature poles will attract or repel the field poles. If the armature is in the positions shown in FIGS. 1 and 3, substantially no rotational torque will be produced by the armature current. However, if the armature is in the position. shown in FIG. 2 rotational torque will be produced and in a direction depending on the direction of current flow. If the current flows in such a direction as to make the upper end of the armature a north pole and the lower end a south pole, the armature will experience clockwise rotational torque. The upper (north) pole of the armature will be repelled by the north pole of the field and attracted by the south pole and the lower end will be attracted by the north pole and repelled by the south pole. Thus, a dualforce, attraction and repulsion will be exerted on both ends of the armature resulting in a.

strong clockwise rotational force or torque. If the current in the armature is reversed, the process is reversed and the armature is driven in a counter-clockwise direction.

FIGS. 4, 5 and 6show the invention including armature windings and hard stops to limit the motion to the most useful angular range (up to approximately degrees). In FIG. 4 armature 1 is provided with windings 4 and 5 and. a member 6 attached to the armature for contacting stop 7 thereby preventing further rotation in a counter-clockwise direction (and stop 8 for limiting rotation in a clockwise direction. While no source of driving current is shown connected to coils 4 and 5, it

is applied from a suitable source of direct current (see FIGS. 10 and 12 also) through directly connecting leads or by means of brushes and commutator segments (as, for example, shown in FIGS. 8, 9, l1 and 13). As stated above, if current is passed through one or both of coils 4 and 5 making the upper end of armature l a north pole, the armature will be forced into clockwise rotation starting with repulsion forces between both ends of the armature and the like poles of the field magnets.

FIG. 5 shows the armature mid-way between its extreme rotational positions and being both pushed by the like poles and pulled by the unlike poles. This may be compared with the situation described in FIG. 2 where without electromagnetic action, the mid-way position is one of inherent instability.

FIG. 6 shows the armature rotated against stop 8 and in its extreme clockwise position. It should be noted that without any armature current being applied both clockwise and counter-clockwise extreme positions having a holding force due to the attraction of the field poles to the soft iron armature. In some applications this natural holding force is sufficient for a latching action. To return the armature from its position shown in FIG. 6 to its initial position as shown in FIG. 4, it is merely necessary to reverse the direction of flow of current in the armature coil or coils. There are two good ways to do this (there are more ways), as by providing coils 4 and 5 wound in opposite directions and merely switching the source of direct current from one coil to another as indicated in FIG. 10; or the polarity of the armature current may be reversed as by a double pole double throw reversing switch.

FIG. 7 shows a sector motor in which the armature is a permanent magnet and the field is a soft iron electromagnet. The permanent magnet armature 9 comprising north and south poles is deposed between poles l0 and 11 of an electromagnetic field. Driving energy is supplied to field coil 12 from a suitable source such as battery 13 through on-off switch 14. The same stop arrangement as shown in FIGS. 4-6 and described above is used. In order to cause counter-clockwise rotation, current is passed through coil 12 in such a direction as to make field pole 11 north and field pole 10 south so that the upper armature pole being north is repulsed by pole 11 and attracted by pole l0 and the lower armature pole being south is repulsed by field pole 10 and is attracted by field pole 11. To reverse the direction of travel, battery 13 is reversed or alternately coil 12 may be provided in two parts in reversed directions as shown in FIG. 10.

While no devices are shown connected to the sector motors shown and described above and to be described below, it will be understood that devices to be actuated may be directly connected to armature l (or 9) or may be driven through. gears, belts or any other suitable means for transmitting the rotational motion. The high starting torque and high efficiency of the present invention lends it to many applications wherein the actuated device is directly connected to the armature shaft. The angle of rotation is determined by the angular separation between stops (such as 7 and 8 in FIGS. 4-6).

FIGS. 8 and 9 show another form of the latching mode of operation using forward and reverse coils on the armature and three brushes and three commutator segments for supplying driving current to the armature. FIG. 10 is the equivalent circuit showing schematically that armature coils 4 and 5 are wound in opposite directions. Now one end (common) of coils 4 and 5 are connected to commutator segment 17; the other end of coil 4 is connected to commutator segment 15; and the other end of coil 5 is connected to commutator segment l6. Brush 19 makes contact with segment 17 and brush 20 makes contact with segment 16. If switch 24-25 is closed completing the circuit of a suitable current source as battery 21 to brush l9 and to brush 20, and provided the direction of winding 5 is correct, current will flow through winding 5 making the left hand end of armature l a north pole and the right hand end a south pole so that the armature reacting with the field poles 2 and 3 will receive a clockwise torque. It is assumed that the position of the armature shown in FIG. 8 is a suitable maximum counter-clockwise position as determined by a stop as described above. The armature will now rotate clockwise to the maximum stop determined position as shown in FIG. 9. When this position is reached, the drive circuit is opened by the over travel of brush 20 which leaves segment 16. This is also a latching position since the field poles acting on the unexcited armature exerts a clockwise holding force. Also, in this position brush 18 contacts segment 15 so that, if switch 22-23 is closed, current is applied to reversed coil 4 and the armature l experiences a counterclockwise torque and armature l returns to its initial position as shown in FIG. 8.

FIGS. ll, 12 and 13 show still another arrangement which may be called fail-safe since it is so organized that in case of a failure of the current source or the coil circuits, the armature 1 will be returned to its initial position by the action of the field poles on the armature. FIG. 12 shows the equivalent circuit with winding 4 a drive coil and winding 26 being a high resistance, low current holding winding. Turning to FIG. 11 commutator segments 34, 36 and 37 and brushes 33 and 35 are provided. Winding 4 is connected between segments 34 and 36 and winding 26 is connected between segments 36 and 37. FIG. 11 also represents the initial position of the armature l, which will be held in this position by the attraction of field poles 2 and 3 and without current passing through the armature windings.

Now, if switches 28-29 and 30-31 are closed, exciting current will flow through brushes 33 and 35, commutator segments 34 and 36 and armature winding 4. If winding 4 is properly wound the left hand end of armature 1 will be made a north pole, the right hand end will be made a south pole and the torque on the armature will be clockwise. This will rotate armature l to the position shown in FIG. 13 where it is stopped by an appropriate stop and switch 30-31 will be opened as by being located at the stop and being operated by the stop arm on the armature (see 6 in FIG. 4). This switch being now open allows holding current to flow through winding 26 and armature I will be held in its extreme clockwise position electromagnetically. However, if the current is interrupted for any reason, armature 1 will be returned to its initial position as shown in FIG. 11 by the magnetic attraction of field poles 2 and 3 acting on the soft iron armature (fail-safe action).

The invention claimed is:

1. A rotary actuator comprising an armature journaled for angular rotation,

a permanent magnetic first stator pole of one polarity and a permanent magnetic second stator pole of opposite polarity from said first polarity said first and said second stator poles surrounding said armature; said armature comprising first and second arms made of magnetic material defining poles which are radially spaced from said stator poles; mechanical stop means for limiting the angular rotation of said armature,- said stop means comprising a first stop and a second stop angularly spaced apart less than 180, with said first armature pole abutting said first stop, and motive means connected to said armature for applying torque to angularly rotate same whereby the application of torque suppliedby said motive means to said armaturewill cause rotation of said first armature pole from said first stop through an angle where said first armature pole remains latched to said first stator pole and thereby cause said first armature pole to return to said first stop when the torque is removed from said armature and rotation of said first armature pole from said first stop by the application of torque by said motive means through an angle equal to or less than the angle between said first and second stops whereby said first armature pole is latched to said second stator pole thereby causing said first armature pole to abut said second stop when said torque from said motive means is removed.

2. A rotary actuator as recited in claim 1 wherein said motive means comprises to windings mounted on said armature, one of said windings providing driving power to rotate said armature such that said first armature pole abuts said second stop and the other of said windings provides power to hold said first armature pole against said second stop.

3. A rotary actuator as recited in claim 1 wherein said motive means comprises two windings mounted on said armature and wound in opposite directions to provide clockwise and c0unter-clockwise torque on said armature.'

4. A rotary actuator as recited in claim 1 wherein said motive means comprises two windings mounted on said armature and wound in the same direction and further including a switch means for reversing the current in said windings and thereby provide clockwise and counterclockwise rotation of said armature. 

1. A rotary actuator comprising an armature journaled for angular rotation, a permanent magnetic first stator pole of one polarity and a permanent magnetic second stator pole of opposite polarity from said first polarity said first and said second stator poles surrounding said armature; said armature comprising first and second arms made of magnetic material defining poles which are radially spaced from said stator poles; a mechanical stop means for limiting the angular rotation of said armature, said stop means comprising a first stop and a second stop angularly spaced apart less than 180*, with said first armature pole abutting said first stop, and a motive means connected to said armature for applying torque to angularly rotate same whereby the application of torque supplied by said motive means to said armature will cause rotation of said first armature pole from said first stop through an angle where said first armature pole remains latched to said first stator pole and thereby cause said first armature pole to return to said first stop when the torque is rEmoved from said armature and rotation of said first armature pole from said first stop by the application of torque by said motive means through an angle equal to or less than the angle between said first and second stops whereby said first armature pole is latched to said second stator pole thereby causing said first armature pole to abut said second stop when said torque from said motive means is removed.
 2. A rotary actuator as recited in claim 1 wherein said motive means comprises to windings mounted on said armature, one of said windings providing driving power to rotate said armature such that said first armature pole abuts said second stop and the other of said windings provides power to hold said first armature pole against said second stop.
 3. A rotary actuator as recited in claim 1 wherein said motive means comprises two windings mounted on said armature and wound in opposite directions to provide clockwise and counter-clockwise torque on said armature.
 4. A rotary actuator as recited in claim 1 wherein said motive means comprises two windings mounted on said armature and wound in the same direction and further including a switch means for reversing the current in said windings and thereby provide clockwise and counter-clockwise rotation of said armature. 